JP2951078B2 - Method for treating aromatic polyamide fiber - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for treating an aromatic polyamide fiber as a reinforcing fiber for a power transmission belt. In particular, the present invention relates to a belt having a form in which aromatic polyamide fibers for belt reinforcement are exposed from a side surface of the belt, such as a timing belt and a low edge V belt, and is formed into a tubular shape and vulcanized aromatic polyamide fiber reinforced rubber. When forming a belt by cutting the composite in a ring shape, the aromatic polyamide fiber exposed on the end face of the belt cut in the fiber axis direction does not fray a single yarn and has good adhesion to the matrix rubber. The present invention relates to a method for treating an aromatic polyamide fiber.

[0002]

2. Description of the Related Art Aromatic polyamide fibers generally have excellent properties such as strength, elastic modulus, dimensional stability, heat resistance and the like, so that rubber composites such as tires, belts and hoses used under severe conditions are used. It is useful as an excellent reinforcing fiber.
In particular, aromatic polyamide fibers are increasingly expected as lightweight reinforcing fibers replacing steel and wires because of their high specific strength and specific elastic modulus.

Generally, when an aromatic polyamide fiber is used as a reinforcing fiber for a timing belt or a low-edge V-belt, the aromatic polyamide fiber is formed into a tubular shape in advance, and is cut by a cutter from a vulcanized aromatic polyamide fiber-reinforced rubber composite in a ring-shape. The belt is formed by doing this, and at that time, a single yarn is frayed from the aromatic polyamide fiber exposed on the cut surface,
It may protrude from the side of the belt, and the quality of the belt is significantly reduced. If the belt is operated on a pulley as it is, the single thread frayed portion may be rubbed by the pulley and the frayed single yarn may be scattered, or the fraying may cause the durability of the belt to be reduced.

[0004] These drawbacks are prevented by the operation of mechanically removing or cutting each of the frayed single yarns during the belt production process. Productivity has declined significantly and has been a major obstacle to adapting aromatic polyamide fibers to this field. On the other hand, in order to improve such disadvantages of the aromatic polyamide, an attempt has been made to treat the aromatic polyamide fiber with a treating agent to prevent fraying of a single yarn at the time of cutting (Japanese Patent Laid-Open No. Hei 1-207480). However, satisfactory results have not been obtained due to other drawbacks, such as lowering the inherent strength of the aromatic polyamide fiber and impairing the adhesiveness and durability.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method for treating an aromatic polyamide fiber to obtain a power transmission belt which has solved the problems in the prior art. That is, an object of the present invention is to provide a processing method that prevents fraying of a single yarn of an aromatic polyamide fiber exposed on an end face of a belt at the time of forming a belt, improves adhesion to a matrix rubber, and does not reduce fatigue.

[0006]

According to the present invention, there is provided a method for treating an aromatic polyamide fiber, wherein the aromatic polyamide fiber is a liquid rubber (A) having hydroxyl groups at both ends and having a molecular weight of 500 to 10,000 and an isocyanate at both ends. Treated with a treating agent containing a liquid rubber (B) having a molecular weight of 500 to 10,000 as a base and an antioxidant,
Heat treatment for 0 seconds, then 1 ≦ K ≦ 5 (K = (T × D
^1/2 ) / 2874, K: twist coefficient, D: denier), and a twisting treatment, followed by applying an adhesive to the aromatic polyamide fiber.

The aromatic polyamide fiber in the present invention means a fiber made of a polymer in which the repeating unit having an aromatic ring accounts for at least 80% of the whole. For example, one of the repeating units represented by the following general formula:
Examples of the polymer include a polymer composed of a kind or two or more kinds, or a fiber composed of a copolymer.

[0008]

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Here, R ₁ and R ₂ may be the same or different and are selected from a hydrogen atom and an alkyl group having 5 or less carbon atoms. Examples of the alkyl group having 5 or less carbon atoms include a methyl group, an ethyl group, a propyl group, a butyl group, and a pentyl group, and are preferably a hydrogen atom. In addition, the following general formula can be exemplified as Ar.

[0010]

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Examples of the aromatic ring include 1,4-phenylene group, 1,3-phenylene group, 4,4'-biphenylene group, 1,5-naphthylene group, 2,6-naphthylene group,
Examples thereof include a 2,5-pyridylene group and the like, and preferably a 1,4-phenylene group.

The aromatic ring includes, for example, a halogen group (eg, chlorine, bromine, fluorine), a lower alkyl group (methyl group, ethyl group, isopropyl group, n-propyl group), a lower alkoxy group (methoxy group, ethoxy group), It may contain a cyano group, an acetyl group, a nitro group or the like as a substituent.

[0013] As typical examples of fibers comprising these polymers or copolymers, polyparaaminobenzamide,
Fibers made of polyparaphenylene terephthalamide, polyparaaminobenzhydrazide terephthalamide, polyterephthalic hydrazide, polymetaphenylene isophthalamide, or the like, or a copolymer of these can be used.

The liquid rubber used in the present invention is referred to as a telekey liquid rubber having a functional group at a molecular terminal, and has a molecular weight of 500 to 10,000 at both ends having hydroxyl groups.
Examples of the liquid rubber of No. 00 include polybutadiene, polyisoprene, polyisoprene, polychloroprene, poly-1,3-pentadiene, polycyclopentadiene, etc. of type 1, type 2, type 1, or a mixture of both types. Moreover, the molecular weight whose both terminals are isocyanate groups is 500 to 10,000.
The liquid rubber having a basic chemical structure of the same kind as the liquid rubber having hydroxyl groups at both ends can also be used as the liquid rubber. Dibutyltin dilaurate may be added as a reaction catalyst between the hydroxyl group and the isocyanate.

Examples of the antioxidant include hindered phenol compounds, amine compounds, phosphorus compounds and sulfur compounds. Representative examples of the hindered phenol compounds include triethylene glycol-bis [3- (3-tert-butyl-6-methyl-4-hydroxyphenyl) propionate] and 1,6-hexanediol-bis [ 3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate], 2,4-bis- (n
-Octylthio) -6- (4-hydroxy-3,5-di-t-butylanilino) -1,3,5-triazine, pentaerythrityl-tetrakis [3- (3,5-di-t
-Butyl-4-hydroxyphenyl) propionate], 2,2-thio-diethylenebis [3- (3,5-
Di-tert-butyl-4-hydroxyphenyl) propionate], octadecyl-3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate, N, N '
-Hexamethylenebis (3,5-di-t-butyl-4-)
Hydroxy-hydrocinnamide), 1,3,5-trimethyl-2,4,6-tris (3,5-di-tert-butyl-4-hydroxybenzyl) benzene and the like. Examples of hindered phenol compounds containing sulfur or phosphorus in the molecule include 2,2-thiobis (4-methyl-6-tert-butylphenol) and 3,5-di-tert-butyl-4-hydroxybenzylphospho. And diethyl etherate.

Representative examples of the amine-based antioxidants include N, N'-di-sec-butyl-p-phenylenediamine and alkylated diphenylamine.

Examples of the phosphite-based antioxidant containing phosphorus include trisnonylphenyl phosphite, triphenyl phosphite, and tris (2,4-di-t-butylphenyl) phosphite. Examples of the sulfur-based antioxidants include dibutyl-3,3'-thiodipropionate, dimistyl-3,3'-thiodipropionate, distearyl-3,3'-thiodipropionate, and pentaerythrityl. -Tetrakis- (3-laurylthiopropionate), ditridecyl-3,3'-thiodipropionate and the like.

As the third component, an epoxy compound can be mixed and used. As the epoxy compound, at least two or more epoxy groups in one molecule are the same as those of the compound 1.
It is a compound containing at least 0.2 g equivalent per 100 g. -Hydroxyphenyl) dimethylmethane, a reaction product of polyhydric phenols such as phenol-formaldehyde resin, resorcin-formaldehyde resin and the above-mentioned halogen-containing epoxides, obtained by oxidizing unsaturated compounds with peracetic acid or hydrogen peroxide or the like. Polyepoxide compound, ie, 3,
4-epoxycyclohexene epoxide, 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexenecarboxylate, bis (3,4-epoxy-6
-Methyl-cyclohexylmethyl) adipate and the like. Among them, a reaction product of a polyhydric alcohol and epichlorohydrin, that is, a polyglycidyl ether compound of a polyhydric alcohol is particularly preferred because it exhibits excellent performance. The treatment of the aromatic polyamide fiber with a treatment agent comprising a liquid rubber (A) having both hydroxyl groups, a liquid rubber (B) having both isocyanate groups and an antioxidant for rubber (C) is substantially carried out. It is preferable to carry out in a non-twisted state. This is to make the liquid rubber uniformly adhere to each single yarn. Once the liquid rubber is applied by twisting, the permeability into the cord tends to be insufficient, it does not adhere uniformly to the single yarn, and the bunching property tends to be poor. Therefore, it is preferable that the application of the liquid rubber to the aromatic polyamide fiber is performed substantially without twist.

The mixing ratio between the liquid rubber (A) having both ends hydroxyl groups and the liquid rubber having both ends isocyanate groups is in the range of 0.5 ≦ (A) / (B) ≦ 4 (weight ratio). Is preferred. When there are many liquid rubbers having hydroxyl groups at both ends, the adhesiveness of the aromatic polyamide fiber is increased and the strength is sufficiently exhibited, but the adhesion to the matrix rubber is not exhibited and the effect of preventing fraying is insufficient. Conversely, if the amount of the liquid rubber having both isocyanate groups at both ends is large, the treated aromatic polyamide fiber becomes hard, and the utilization rate of strength at the time of twisting becomes low. The adhesion rate to the aromatic polyamide fiber is 1 to
25% is preferred. Further, it is preferably 5 to 20%. When the adhesion rate is lower than 1%, when the aromatic polyamide fiber is used as the reinforcing fiber of the power transmission belt, the single yarn exposed from the end face of the belt may be frayed. The strength utilization rate at the time of twisting the aromatic polyamide fiber is low, and the strength is not sufficiently exhibited.

The rubber antioxidant (C) is 0.00
It is added so that 5 ≦ (C) / [(A) + (B)] ≦ 0.05. Preferably 0.01 ≦ (C) / [(A)
+ (B)] ≦ 0.03.

When adding the epoxy compound (D),
0.01 ≦ (D) / [(A) + (B) + (C)] ≦ 0.
Adjustment to 10 is preferred.

The above-mentioned liquid rubber (A) having both ends hydroxyl groups and the liquid rubber (B) having both ends isocyanates
And a mixture with an antioxidant (C) for rubber is applied to the aromatic polyamide fiber, and subsequently at 150 to 250 ° C for 30 to 30 ° C.
Treat for 210 seconds. Preferably, it is 60 to 180 seconds. If the treatment temperature is lower than 150 ° C. and shorter than 30 seconds, the reaction does not proceed sufficiently and the bunching effect is poor, causing the single yarn to fray and the adhesion to the rubber matrix to be lowered. Further, if the treatment temperature exceeds 250 ° C. and the treatment is performed for more than 210 seconds, the reaction proceeds too much, and the aromatic polyamide fiber becomes extremely hard. It is not preferable as a reinforcing fiber.

The aromatic polyamide fiber treated in this manner continues to have ≦ K ≦ 5 (K = (T × D ^1/2 ) / 2
874, where K is a twist coefficient, T is the number of twists per meter, and D represents denier). If the twist coefficient is less than 1, the end face may fray when used as a reinforcing material for a power transmission belt. Conversely, if the twist coefficient is more than 5, the strength reduction due to the twisted yarn is large and the elongation is large, and the power transmission belt is large. Is not preferred as a reinforcing fiber for use.

In the twisting treatment, the untwisted yarn is substantially twisted,
Next, it is preferable to perform the twisting in a direction opposite to the twisting, but it is also possible to use the twisting only as the reinforcing fiber without the twisting. Next, the twisted aromatic polyamide fiber is RFL
Treated with an adhesive containing. RFL preferably has a molar ratio of resorcinol to formaldehyde of 1: 0.1 to 1: 8. Further, it is preferably used in the range of 1: 0.5 to 1: 5, particularly preferably in the range of 1: 1 to 1: 4.

Examples of the rubber latex include natural rubber latex, styrene / butadiene copolymer latex, vinylpyridine / styrene / butadiene / terpolymer latex, nitrile rubber latex, hydrogenated nitrile rubber latex, chlorosulfonated polyethylene latex, and chloroprene rubber latex. These are used alone or in combination. The type of latex is selected according to the rubber matrix used. In addition, as shown in JP-B-57-53912, the general formula

[0026]

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The ethylene urea compound represented by the formula (1) may be added for use. The ethylene urea compound is usually added in the form of an aqueous dispersion in an amount of 0.5 to 30% by weight based on RFL. R
After the treatment with FL, it may be further treated with rubber paste.

After the RFL treatment, at 80 to 150 ° C., 0.5
After drying for ~ 300 seconds, at 150 ~ 260 ° C, 0.5 ~ 5
It is desirable to heat and cure for a minute. The amount of RFL attached to the twisted cord is adjusted to 1 to 10%.

By treating the aromatic polyamide fiber by the treatment method of the present invention, it is possible to prevent single yarn fraying from the end face of the aromatic polyamide fiber reinforced power transmission belt, and to prevent the matrix rubber from being frayed. Can be improved. This is because a liquid rubber having hydroxyl groups at both ends reacts with a liquid rubber having isocyanate groups at both ends to form a urethane film having a high cohesive force, and this film solidifies a single yarn of aromatic polyamide fiber. It is presumed that the anti-fraying property is improved due to the adhesion to the surface. On the other hand, adhesion is good because RFL reacts with a urethane bond or a terminal group, or a cross-link between a double bond contained in urethane and RFL, or wettability with RFL is improved, so that good results can be obtained. It is estimated to be. The effect of the antioxidant is that the double bonds contained in the liquid rubber are oxidized or crosslinked by heat treatment,
By reducing the number of double bonds and preventing the cord hardness from increasing, the strength at the time of twisting and the fatigue resistance are prevented, and the RF
It is thought that it increases the interaction with L and contributes to improving the adhesiveness.

[0030]

As described above, the aromatic polyamide fiber treated by the method of the present invention has a small decrease in strength, and does not cause fraying of a single yarn from the belt end face after forming the power transmission belt, and has good adhesiveness and fatigue resistance. Is also good.

Hereinafter, the present invention will be described specifically with reference to examples.

In the examples, the fraying property, the cord peeling adhesive strength, the T adhesive strength, and the strength retention during fatigue are values obtained as follows.

(1) Frayability The frayed aromatic polyamide cord of the present invention is sandwiched between two rubber sheets having a thickness of about 2 mm.
The rubber was vulcanized at 150 ° C. for 30 minutes under a pressing pressure of 50 kg / cm ² to obtain a rubber sheet. This sheet was cut in the length direction of the cords arranged in the rubber using a cutter knife so that the end faces of the cords appeared on the cut surface. Then, the state of the single yarn of the aromatic polyamide fiber protruding from the end face was visually determined. In addition, this end face is sandpaper (# AA-
150), and the frayed state of the single yarn was observed. The evaluation was (good) ◎ → ○ → △ → × (poor).

(2) Peeling adhesive strength of cord This shows the peeling adhesive strength between the treated cord and rubber. 7 cords are buried near the surface of the rubber sheet.
Vulcanization was performed at a pressing pressure of 50 kg / cm ² for 0 minute, then the two cords at both ends were removed, and the force required to peel off the remaining five cords from the rubber sheet at a speed of 200 mm / min was given by kg / 5. Displayed in the book.

(3) T-adhesive strength This indicates the shear adhesive strength between the treated cord and rubber. The cord is embedded in a rubber block, vulcanized at 150 ° C. for 30 minutes at a pressing pressure of 5 kg / cm ² , and then the cord is pulled out of the rubber block at a speed of 200 mm / min. displayed.

(4) Fatigue strength retention This is a measure of fatigue resistance. Using a belt-type fatigue tester, a cord is sandwiched between two rubber sheets having a thickness of 2 mm and vulcanized at 150 ° C. for 30 minutes at a pressure of 50 kg / cm ² to obtain a sheet having a width of 50 mm × 500 mm. Apply a load of 25 kg to the test sample cut into a belt shape of
Attach it to a roller of φ.
After reciprocating at 0 rpm and repeating 500,000 times, the cord was taken out from the test sample, and the residual strength was measured to obtain the strength retention rate during fatigue.

[0037]

Examples 1-4, Comparative Examples 1-3 "Technola" type T-200 manufactured by Teijin Limited as aromatic polyamide fiber.
(1500 denier / 1000 filaments) was used. As a liquid rubber (A) having both ends hydroxyl groups, a liquid 1,2-polybutadiene glycol having a molecular weight of 3000 (G-3000 manufactured by Nippon Soda Kogyo Co., Ltd.), and as a liquid rubber (B) having both ends isocyanate groups , Liquid 1,
A predetermined amount of a 50% MEK solution of type 2 polybutadiene diisocyanate (TP1001 manufactured by Nippon Soda Kogyo Co., Ltd.) was weighed and dissolved in toluene. Then, as an antioxidant, 1,3,5-trimethyl-2,4,6-tris-
(3,5-Di-t-butyl-4-hydroxybenzylbenzene (Irganox 1330, manufactured by Ciba-Geigy)
Was added to liquid rubber [(A) + (B)] at 1%. Furthermore,
Glycerin diglycidyl ether (EX313 manufactured by Nagase Kasei Co., Ltd.) was similarly added in an amount of 5%. After preparing a treatment solution having a concentration of 20% as shown in Table 1 as a toluene solution, technolas fibers were immersed. The squeezing pressure was adjusted so that the adhesion rate of the treatment liquid to the fibers was about 10%. 15 for drying
Performed at 0 ° C. for 2 minutes, then cured at 250 ° C. for 1 minute. Thereafter, the treated Technora raw yarn was twisted at a twist factor of 2 while being plied.

Next, the twisted cord is subjected to RFL (R / F =
1/6 molar ratio, RF / L = 1/5 weight ratio, L = vinylpyridine-styrene-butadiene copolymer rubber latex), and adjusted so that the adhesion rate to the twist cord becomes 5%. 2 minutes at 240 ° C
Curing heat treatment for minutes.

The obtained adhesive treatment cords were arranged in parallel on a chloroprene (CR) rubber sheet having a thickness of about 2 mm, and a similar CR rubber sheet was further superimposed on the cords.
The rubber was vulcanized at 50 ° C. for 30 minutes at a pressing pressure of 50 kg / cm ² to obtain a rubber sheet. This sheet was cut in the length direction of the cords arranged in the rubber using a cutter knife so that the end faces of the cords appeared on the cut surface. Then, the state of the single yarn of the aromatic polyamide fiber protruding from the end face was visually determined. Also, this end face is sandpaper (# AA-15)
0), and the frayed state of the single yarn was observed. The evaluation was (good) ◎ → ○ → △ → × (poor).

Next, the peel adhesion, the T adhesion, and the fatigue strength by a belt fatigue tester were measured using the above-described methods. Table 1 shows the results.

As Comparative Example 1, various characteristics of cords obtained without treatment with a treating agent containing a liquid rubber and in the same manner as in the other examples were measured. Table 1 also shows the results. Also, liquid polybutadiene-modified urethane rubber (A)
Table 1 shows the results of only (Comparative Example 2) and only the liquid rubber (B) (Comparative Example 3).

[0042]

[Table 1]

As is clear from Table 1, hot-rolling of aromatic polyamide fibers treated with a liquid polybutadiene composed of a liquid rubber having hydroxyl groups at both ends and a liquid rubber having isocyanate groups at both ends, and a treatment solution containing an antioxidant. It can be seen that the prevention, the adhesion, and the fatigue resistance are good.

[0044]

Examples 5 to 8, Comparative Example 4 Using the treatment liquid of Example 2,
The treatment was carried out in the same manner as in Example 2 except that the addition ratio of the antioxidant was changed to the conditions shown in Table 2. Table 2 shows the results. Table 2 also shows the results of the system without the antioxidant (Comparative Example 4).

[0045]

[Table 2] As can be seen from Table 2, by adding the antioxidant, the fraying property is better as compared with the case without addition,
It can be seen that adhesion and fatigue properties are also improved.

[0046]

Examples 9 to 12 and Comparative Examples 5 to 6 Processing was carried out in the same manner as in Example 1 except that the treatment solution of Example 2 was used and the heat treatment conditions were changed to those shown in Table 3. Table 3 shows the results.

As can be seen from Table 3, 100-260 ° C.
By performing the treatment at the heat treatment temperature described above, it is possible to obtain an aromatic polyamide fiber having good anti-fraying properties, adhesiveness, and fatigue resistance.

[0048]

[Table 3]

──────────────────────────────────────────────────続 き Continued on front page (51) Int.Cl. ⁶ Identification code FI // D06M 101: 36

Claims (5)

(57) [Claims] 1. An aromatic polyamide fiber comprising a liquid rubber (A) having hydroxyl groups at both ends and having a molecular weight of 500 to 10,000 and a molecular rubber having both ends at an isocyanate group having a molecular weight of 500 to 10,000.
000 liquid rubber (B) and a treating agent containing an antioxidant, heat-treated at 100 to 260 ° C. for 30 to 210 seconds, and then 1 ≦ K ≦ 5 (K = (T × D ^1/2 ) / 287
4, K: Twisting coefficient, D: Denier), after twisting, resorcinol-formalin latex (RFL)
A method for treating aromatic polyamide fibers, characterized by applying an adhesive containing: 2. The method for treating an aromatic polyamide fiber according to claim 1, wherein the antioxidant is a hindered phenol compound. 3. The method for treating an aromatic polyamide fiber according to claim 1, wherein the antioxidant is an amine compound. 4. The method for treating an aromatic polyamide fiber according to claim 1, wherein the antioxidant is a phosphorus compound. 5. The method for treating an aromatic polyamide fiber according to claim 1, wherein the antioxidant is a sulfur compound.